Terminal connection device for a power cable

ABSTRACT

A terminal connection device for connecting an end of a medium- or high-voltage power cable to a connection point comprises a) an interface cable having first and second end portions, comprising an inner conductor and a conductive or semiconductive layer; b) a first stress control tube comprising a stress control element, and an insulating layer arranged around the stress control element, wherein the first stress control tube is mounted on the first end portion of the interface cable; c) a first cable connector for connecting the interface cable to the power cable, the first cable connector being connected to the second end portion of the interface cable; and d) one or more tubular shrinkable sleeves, at least a portion of one of the tubular shrinkable sleeves extending over at least a portion of the first stress control tube wherein the portion of the tubular shrinkable sleeve extending over at least a portion of the first stress control tube is shrunk down around at least a portion of the first stress control tube.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a terminal connection device for apower cable, in particular a medium or high voltage power cable, and toa method of connecting an end of a medium or high voltage power cable toa connection point.

Description of the Prior Art

It is generally known to use radially shrinkable sleeves for enclosingan electrical cable connected to another electrical cable or a stop end.An example of a known radially shrinkable sleeve for covering cableterminations either of cable connectors or stop ends is described inEP-B-0 435 569. The shrinkable sleeve comprises a dielectric material asan intermediate insulating layer, an electric field control inner layercombined with a partially coated inner conductive layer, and anelectrically conducting outer layer. Such a multi-layer sleeve ispreferably made by extrusion and preferably comprises silicone or EPDM.

When making cable splices or cable end terminations by means of a knownradially shrinkable sleeve it is necessary that on one side of theconnector a free space is provided (parking position), which correspondsto the complete length of the shrinkable sleeve. After the cableconnection is established, the shrinkable sleeve is centered over thecable connection and is then shrunk down either by the application ofheat or by the removal of an external or internal support maintainingthe shrinkable sleeve in a radially extended state. EP-B-0 541 000discloses a radially shrinkable sleeve which in its radially expandedstate is held by two removable support cores located adjacent eachother. Another radially shrinkable sleeve having individual supportcores for different sections of the sleeve is disclosed in EP-B-0 966780. In this known assembly, different sections of the sleeve areconcentrically arranged by folding back the sleeve, wherein theindividual sections are maintained in their respective radially expandedstates by means of removable support cores or similar support elements.

WO90/13933 discloses a plug-in connection, in particular a sleeve forhigh-voltage plastic cables, comprising an electrical insulator fittingclosely onto cable ends, the cable insulator having an electricallyconducting stress-controlling body for screening cable conductorconnecting elements received herein, an insulating body surrounding thestress-controlling body and an electrically conducting sheathsurrounding the insulating body completely or partially. The insulatoris provided with axial close-fitting passages merging into the space inthe stress-controlling body for the cable conductor connecting elements.The cable conductor connecting elements comprise at least one plug partand at least one counter-plug part and means for mutually locking theplug part and the counter-plug part

WO96/10851 aims to provide a simplified connection system for highvoltage power cables having ratings up to 400 KV and above, inparticular a common cable connection system for all accessories andinterconnection. The connection system uses a generally applicableinterface for interconnection with a number of different apparatus andincludes a cable termination consisting of an elastomeric body,integrated therein is a stress relief device, a connector shield, aninsulation having a conical interface surface and an outer conductivescreen and a rigid insulator having a conical interface surfacecorresponding to the interface surface of the cable termination.

When an existing cable termination has to be replaced with a new one(due to repair/maintenance or feature upgrading) without the need toreplace the existing power cables (i.e., retro-fitting), the mostdifficult operation is to re-connect the existing cables to the newtermination. Replacing a cable termination requires cutting off theexisting cable termination in its installed location. Typically this isa switchgear enclosure, a bus bar cabinet, or adjacent generators,motors, transformers, etc. When the existing cable termination isremoved, the remaining power cable is not long enough to be terminatedwith a standard cable termination and re-connected again to theswitchgear pole, bus bar, generator, etc.

Additionally, when a repair is required, the time it takes to reconnectthe power cable is a concern in terms of impact on service continuityand penalty costs for energy network management.

Accordingly, there is a need for an improved cable termination, inparticular for medium or high voltage power cables, that provides astructural/dimensional solution suitable to be quickly installed andworking inside a very limited space.

SUMMARY OF THE INVENTION

The present invention provides a terminal connection device forconnecting an end of a medium- or high-voltage power cable to aconnection point, the terminal connection device comprising

-   a) an interface cable having first and second end portions,    comprising an inner conductor and a conductive or semiconductive    layer;-   b) a first stress control tube comprising a stress control element,    and an insulating layer arranged around the stress control element,    wherein the first stress control tube is mounted on the first end    portion of the interface cable;-   c) a first cable connector for connecting the interface cable to the    power cable, the first cable connector being connected to the second    end portion of the interface cable; and d) one or more tubular    shrinkable sleeves, at least a portion of one of the tubular    shrinkable sleeves extending over at least a portion of the first    stress control tube wherein the portion of the tubular shrinkable    sleeve extending over at least a portion of the first stress control    tube is shrunk down around at least a portion of the first stress    control tube.

The terminal connection device is effectively an integrated splice andtermination with an interface cable between the two portions. Because ofits integrated features, the terminal connection device allows formaking a quick and straight-forward connection between a cut off powercable and a connection point in a confined space. The terminalconnection device of the present invention facilitates easily connectinga power cable to the device and easily connecting the device to aconnection point. In addition, its integrated features also reduce thepossibility of making mistakes during installation, which canpotentially be an issue with a termination that has many individualelements that must be attached to the cable and/or connection point. Theconnection point may be on a piece of equipment such as a generator ortransformer or may be a switchgear pole or bus bar. In particular, theterminal connection device is useful when an existing terminal device,which connects an installed power cable to a connection point, isremoved by cutting off the portion of the power cable on which theterminal device is installed. The remaining installed cable is then tooshort to reach the connection point. A suitable new terminal device mustbe installed. Because the terminal connection device of the presentinvention may use a section of commercially available cable for itsinterface cable, terminal connection devices of the present inventionmay be easily made in many different lengths and using different typesof power cable without adding additional manufacturing costs and,therefore, can accommodate the needs for a variety of lengths and sizesand types of cable terminal devices.

In the terminal connection device of the present invention, a powercable can very easily be connected to the first cable connector. Thefirst cable connector is fixedly connected and arranged within theterminal connection device. A power cable attached to a mating secondcable connector can be easily connected to the first cable connector inthat the mating second cable connector is inserted into portions of thesecond stress control tube and tubular sleeve that are held in anexpanded state by support cores so as to make electrical connection withthe first cable connector by simply plugging the second cable connectorinto the first cable connector, or vice versa. If an intermediateconnector is used, the second cable connector can just as easily beplugged into the intermediate connector. Additionally, a rigid sleevemay be secured around the first cable connector and may extendsufficiently beyond the mating face of the first cable connector tocover the second cable connector once it is mated to the first cableconnector. Accordingly, no portion of the terminal connection deviceneeds a parking position or any free space on the power cable.

In a specific aspect of the invention, a portion of at least one of thetubular shrinkable sleeves is shrunk down around a portion of theinterface cable.

In another aspect, the tubular shrinkable sleeve extending over at leasta portion of the second stress control tube comprises a portion adaptedto be shrunk down around a portion of the power cable.

In a further aspect, the first end portion of the interface cable isattached to a lug.

In a yet further aspect, the stress control element of one or both ofthe first and second stress control tubes is a geometric stress controlelement or a capacitive stress control element.

In a particular aspect of the invention, the tubular shrinkable sleeveextending over at least a portion of the first stress control tubecomprises, on an outer side, one or more skirts for reducing trackingcurrent.

In another aspect, the interface cable further comprises an insulatinglayer arranged concentrically around at least an axial section of theinner conductor, and the terminal connection device comprises acapacitive voltage sensor including a printed circuit board element. Theprinted circuit board element may be placed over an electricallyisolated piece of conductive or semiconductive material. Theelectrically isolated piece of conductive or semiconductive material maybe arranged on the insulating layer of the interface cable and operableto form an electrode of a sensing capacitor for sensing a voltage of theinner conductor. The insulating layer may be operable to form adielectric of the sensing capacitor.

In a further aspect, the terminal connection device further comprisesadditional semiconductive material, arranged concentrically around atleast an axial section of the insulating layer on either side of theelectrically isolated piece of conductive or semiconductive material.The additional semiconductive material may comprise two semiconductiveaxial sections, electrically isolated from the electrically isolatedpiece of conductive or semiconductive material by non-conductive axialsections.

Some or all of the electrically isolated piece of conductive orsemiconductive material or of the additional semiconductive material maybe affixed adhesively to the insulating layer.

In a specific aspect, the printed circuit board element comprises apatterned gold-plated copper layer in electrical contact with theelectrically isolated piece of conductive or semiconductive material.

In another aspect of the invention, the electrically isolated piece ofconductive or semiconductive material comprises a portion of thesemiconductive layer of the interface cable.

The invention also provides a method of connecting an end of a medium-or high-voltage power cable to a connection point, comprising the stepsof

-   a) providing a terminal connection device as described above;-   b) providing a medium- or high-voltage power cable;-   c) connecting the terminal connection device to the end of the power    cable by connecting the interface cable to the end of the power    cable via the first cable connector; and-   d) connecting the terminal connection device to the connection point    by connecting the first end portion of the interface cable to the    connection point.

In at least one embodiment of the present invention, after the firstcable connector is mated to the second cable connector, the secondstress control tube is shrunk down around the mated connectors and aportion of the power cable, then the portion of a tubular sleeveextending over a portion of the second stress control tube is shrunkdown over the second stress control tube and a portion of the powercable. Because the terminal connection device includes an integratedsplice portion and a termination portion, it allows for easy connectionto the power cable using the splice portion and easy connection to theconnection point using the termination portion.

The first cable connector of the terminal connection device according toat least one embodiment of the invention may be configured as a socketor plug. To ensure that a socket-and-plug connection is capable ofcarrying high electric currents, the prior art offers various contacttechniques as e.g. disclosed in EP-A-0 716 474, DE-A-38 13 001, andDE-A-29 39 600.

If an intermediate connector is used, it can be flexible, partiallyflexible or rigid. A flexible or partially flexible intermediateconnector serves for a facilitated application of a power cable to beconnected to the first cable connector. This is advantageous when usingthe preassembled terminal connection device in a narrow space.

The mechanical and electrical connection between the interface cable andthe second cable and their respective connectors, which in turn are tobe connected to each other, according to one embodiment of the presentinvention, is realized by crimping or fastening screws or similarfastening elements. Preferably, the fastening screws are configured asshearable screws. Examples of fastening elements suitable for theconnection between a cable (or a stop end element) and a second cableconnector are disclosed in WO-A-95/25229, WO-A-96/31706, EP-B-0 470 388,EP-B-0 688 960, EP-B-0 692 643, EP-A-0 769 825, EP-B-0 819 222, EP-B-0984 176, and U.S. Pat. No. 6,045,373.

Generally, both heat and cold shrinkable elements can be used for thepre-assembled terminal connection device according to the invention.However, in order to avoid the application of heat for shrinking downthe tubes and sleeves, cold shrinkable materials are preferred. Thesematerials are generally known in the art, and preferably silicone orEPDM is used. In case of a cold shrinkable sleeve or tube, a portion ofthe sleeve or tube can be held in a radially expanded state by means ofa removable support core. Suitable supports are generally known to thoseskilled in the art. In particular, it is known to use at least onesupport core adapted to be inserted into the cold shrinkable sleeve ortube for holding it in a radially expanded state, and removed from thecold shrinkable sleeve or tube for shrinking down the sleeve or tube. Inat least one embodiment of the present invention, the support core holdsa portion of a stress control tube in a radially expanded state andcomprises a helically wound ribbon that is adapted to be removed fromthe stress control tube by pulling an end of the ribbon that initiateson a first end of the support core through the center of the core andout the second end of the core such that the pulled end of the ribbonseparates from the remainder of the core winding by winding startingfrom the first end of the core. Examples for various supports as well ascores for holding the second tubular portion in a radially expandedstate are disclosed in DE-A-39 43 296, DE,A-42 33 202, WO-A-95/11542,WO-A-95/318 845, EP-A-0 291 213, EP-A-0 399 263, EP-A-0 500 216, EP-A-0631 117, EP-A-0 631 357, EP-A-0 702 444, EP-B-0 966 780, U.S. Pat. Nos.3,515,798, 4,135,553, 4,179,320, 4,503,105, 4,656,070, 5,098,752, and4,585,607.

The second stress control tube can be arranged so as to extend beyondthe first cable connector and/or rigid sleeve prior to the terminalconnection device being connected to a power cable and, accordingly, isheld in a radially expanded state as mentioned before. In an alternativeembodiment, the second stress control tube can be folded back over thefirst cable connector and, if made from a cold shrinkable material, canbe held in a radially expanded state.

The stress control tubes comprise in their mounted state an inner layerwhich is a stress control element and an outer dielectric layer of e.g.silicone or ethylene propylene diene monomer rubber (EPDM). The stresscontrol element may achieve stress control by the use of particularmaterials, such as High K materials or by the use of geometric stresscontrol shapes. The stress control tube of the splice portion typicallyfurther comprises a thin electrically conductive or semiconductive layerinside a portion of the stress control element and a thin electricallyconductive or semiconductive layer outside the dielectric layer. Thosestress control tubes which can be a push-on type or can be made of heator cold shrinkable materials are generally known to those skilled in theart. They may be fabricated by a molding process or an extrusionprocess. To obtain a stress control tube with two layers, a standardcoextrusion process may be used, e.g. the inner electrically conductiveor semi conductive layer and the outer dielectric layer are extrudedtogether. An example of a suitable molded stress control tube isdescribed and illustrated in WO97/08801.

It is normally necessary to use one tubular sleeve for a splice and onetubular sleeve for a termination. This can be done in the terminalconnection device of the present invention in which separate tubularsleeves cover the splice and termination portions of the device.Alternatively, a single tubular sleeve may cover both the splice andtermination portions of the device. If two separate tubular sleeves areused, they may overlap between the two portions, typically over aportion of the interface cable. It is also possible to arrange the twotubular sleeves so that they don't overlap. In this case, the outerinsulative jacket typically needs to remain in the exposed portion ofthe interface cable or the interface cable needs to be insulated with athird tubular sleeve or some other type of insulating material. If theterminal connection device uses a particularly long piece of cable forthe interface cable, it may be most efficient and economical to leavethe insulating jacket on the interface cable.

In at least one embodiment of the present invention, the terminalconnection device is pre-assembled in that the first cable connector andthe interface cable are fixedly arranged in the stress control tubes andan outer tubular sleeve prior to the use of the terminal connectiondevice for connecting to and terminating a power cable. Pre-assemblingis advantageous in that it may make field assembly obsolete. Fieldassembly of a terminal connection device may be difficult, because theinterface cable, which may be relatively short, needs to be stripped andprepared for mounting the stress control tubes and the first cableconnector. Preparing the interface cable and mounting stress controltubes and the first cable connector on it in the field poses anincreased risk of having dirt particles and air pockets entrappedbetween layers of the terminal connection device. These particles andair pockets may lead to partial discharges and potential damage to theterminal connection device.

In a further embodiment of the invention, one or more sensors may beintegrated into the terminal connection device. Such sensors can be usedto sense, measure, record and save or transmit information regarding thecondition or operation of the power cable such as current, voltage,temperature, etc. The sensor can be integrated in the terminalconnection device of the invention during its construction. A preferredlocation for the integration of the sensor would be the area between theconnector and termination sections or in the termination section. Thesensor will typically include some type of information transmissionsystem to transmit the information to an external information collectingand/or processing device. The transmission system may be any suitablesystem including hard wiring or a wireless transmission system. Thesensor may be located on a layer of conductive or semiconductivematerial that is electrically isolated from the conductive orsemiconductive layer of the interface cable. However, a ground currentneeds to be established across the sensor. To achieve this, a portion ofthe semiconductive layer may be isolated by removing two annularsections of the semiconductive layer of the interface cable on each sideof the portion to be isolated. The sensor is then mounted on andconnected to this isolated portion, an insulating material is placedover the sensor and a conductive or semiconductive material is placedover the insulating material to shield the sensor against externalelectrical fields. Instead of using the interface cable semiconductivelayer, the area may be stripped of the cable semiconductive layer and apatch of conductive or semiconductive material may be placed on theinsulation layer, e.g., by adhering it to the insulation layer of theinterface cable. One sensor might be a capacitive voltage sensor placedover an electrically isolated piece of conductive or semiconductivematerial with the conductive or semiconductive material arranged on theinsulating layer of the interface cable and operable to form anelectrode of a sensing capacitor for sensing a voltage of the innerconductor of the interface cable. The insulating layer of the interfacecable is operable to form a dielectric of the sensing capacitor.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, enabling one of ordinary skill in the art to carryout the invention, is set forth in greater detail in the followingdescription, with reference to the accompanying drawings in which

FIG. 1 is a cross-sectional view of a first embodiment of a terminalconnection device of the present invention,

FIG. 2 is a cross-sectional view of an alternate embodiment of theterminal connection device according to FIG. 1,

FIG. 3 is a cross-sectional view of a splice portion of a terminalconnection device of at least one embodiment of the present invention,

FIG. 4 shows a cross-sectional view of a termination portion of aterminal connection device of at least one embodiment of the presentinvention,

FIG. 5 shows a partial cross-sectional view of a termination portion ofa terminal connection device of at least one embodiment of the presentinvention, wherein the termination portion includes sensor devices.

DESCRIPTION OF PREFERRED EMBODIMENTS

Herein below diverse embodiments of the present invention are describedand shown in the drawings wherein like elements are provided with thesame reference numerals.

FIG. 1 shows a first embodiment of a pre-assembled terminal connectiondevice for connecting an end of a medium- or high-voltage power cable toa connection point. The pre-assembled terminal connection device 10comprises an interface cable 12 having an inner conductor 14, aninsulation layer 16 surrounding conductor 14, and a conductive orsemiconductor layer (hereinafter referred to as semiconductor layer) 18surrounding insulation layer 16. As illustrated in FIG. 1, anyadditional layers of the interface cable 12, such as a metallic cablescreen surrounding semiconductor layer 18 and an outer cable jacketsurrounding the metallic cable screen are typically removed. However, insome embodiments, these layers may remain on a portion of interfacecable 12. Terminal connection device 10 is effectively comprised of asplice portion 20 and a termination portion 22. In some embodiments anintermediate portion between the splice and termination portions mayexist.

In the splice portion 20 of terminal connection device 10, a first cableconnector 24 is attached to one end of inner conductor 14 of interfacecable 12. It may be attached by any suitable method such as by crimpingor with screws. First cable connector 24 is configured to mate withsecond cable connector 26, which is not part of the pre-assembledterminal connection device 10. For example, first cable connector 24 maybe a socket connector and second cable connector 26 may be a plugconnector. First cable connector 24 may optionally be enclosed by, andoptionally secured within, rigid sleeve 28, which may be insulative,conductive, or semiconductive. Rigid sleeve 28 may optionally extendbeyond the mating face of first cable connector 24 such that when firstand second cable connectors 24 and 26 are mated, second cable connector26 is also enclosed by rigid sleeve 28. Connector 26 is attached to theinner conductor 44 of a power cable 42. Inner conductor 44 is surroundedby insulating layer 46, which is surrounded by conductive orsemiconductive layer 48. Connector 24 may have a pawl 30 that engageswith a notch 32 is rigid sleeve 28 to hold connector 24 securely withinrigid sleeve 28. Other suitable means known in the art may be used tosecure connector 24 in rigid sleeve 28.

In the termination portion 22 of terminal connection device 10, a lug 34is typically attached to the end of inner conductor 14 of the interfacecable 12 opposite the end attached to connector 24. Semiconductor layer18 is stripped away from the end of interface cable 12 thereby exposinginsulation layer 16. A first stress control tube 36 comprising an innerHigh K layer 38 and an outer insulation layer 40 is mounted on the endportion of interface cable 12 adjacent lug 34 and extends along theterminal portion 22 of terminal connection device 10 such that itoverlaps a portion of semiconductive layer 18 of interface cable 12.First stress control tube 36 is made of a shrinkable material, typicallysilicone or EPDM. It may be heat or cold shrinkable material. As shownin FIG. 1, it is shrunk down over the termination portion 22 of terminalconnection device 10.

As shown in FIG. 1 a second stress control tube 36′ extends along thesplice portion of connector 10, including over connector 24 and is madelong enough to cover connector 26 and a portion of power cable 42 towhich connector 26 is attached when the terminal connection device 10has been fully installed. Similar to first stress control tube 36,second stress control tube 36′ is made of a shrinkable material,typically silicone or EPDM. It may be heat or cold shrinkable material,but is shown as a cold shrinkable material in FIG. 1. Second stresscontrol tube 36′ differs from first stress control tube 36 in that ithas a thin inner semiconductor layer (not shown) inside of stresscontrol layer 38 along the portion of stress control layer 38 that willcover connectors 24 and 26. The length of the thin inner semiconductorlayer is sufficient that it covers a portion of insulation layer 16 ofinterface cable 12 and a portion of insulation layer 46 of power cable42 when terminal connection device 10 is fully installed. The thin innersemiconductor layer may be painted on the interior surface of stresscontrol layer 38 or may be a separate layer of material. Stress controltube 36′ also differs from stress control tube 36 in that it has a thinouter semiconductive layer (not shown) on the outside of insulationlayer 40. The thin outer semiconductive layer extends along the entirelength of insulation layer 40 of stress control tube 36′. The thin outersemiconductor layer may be painted on the exterior surface of insulationlayer 40 or may be a separate layer of material.

As further illustrated in FIG. 1, prior to the mating of first andsecond cable connectors 24 and 26, a support core 50 is placed withinthe portion of second stress control tube 36′ that will cover powercable 42. Support core 50 holds this portion of second stress controltube 36′ in an expanded state to allow the easy insertion of connector26 into rigid sleeve 28 so that it can securely mate with connector 24.In the embodiment of FIG. 1, terminal connection device 10 furthercomprises a single tubular sleeve 52 that extends over both the spliceand termination portions 20, 22. Tubular sleeve 52 comprises aninsulating layer. Between tubular sleeve 52 and second stress controltube 36′ there is typically a “sock” 54 made of conducting orsemiconducting material. Its purpose is to establish an electricalconnection between semiconductive layers 18 and 48 of interface cable 12and power cable 42, respectively, when terminal connection device 10 isfully installed and to maintain the thin outer semiconductive layer (notshown) of second stress control tube 36′ at ground potential across thesplice. In the embodiment illustrated in FIG. 1, tubular sleeve 52 ispositioned over the entire length of first and second stress controltubes 36 and 36′ as well as the portion of interface cable 12 that isnot surrounded by either stress control tube. Tubular sleeve 52 is madeof a shrinkable material, typically silicone or EPDM. It may be heat orcold shrinkable material, but is shown as a cold shrinkable material inFIG. 1. In the illustrated embodiment, tubular sleeve 52 includes skirts56 in the termination portion of terminal connection device 10. Theskirts serve to reduce tracking current and are usually used only onoutdoor termination devices.

As further illustrated in FIG. 1, prior to the mating of first andsecond cable connectors 24 and 26, a support core 58 is placed aroundthe portion of second stress control tube 36′ that is held in anexpanded state by support core 50 and a portion of tubular sleeve 52 isfolded back over support core 58. This folded back portion of tubularsleeve 52 will cover power cable 42 when the terminal connection device10 is fully installed.

Support cores 50 and 58 as well as other support cores described hereinmay be any suitable type of support core, but will typically comprise ahelically wound ribbon that is removed by unwinding the ribbon such thatthe cold shrinkable material shrinks down over power cable 42 startingat the cable end attached to conductor 26. This support core techniqueis generally known to those skilled in the art.

The embodiment illustrated in FIG. 2 is similar to the embodiment ofFIG. 1 except that tubular sleeve 52 comprises two separate parts, 52′and 52″. In the embodiment of FIG. 2, parts 52′ and 52″ have overlappingportions. In an alternate embodiment (not illustrated), parts 52′ and52″ do not overlap. In such an embodiment, the portion of interfacecable 12 not covered by a tubular sleeve will have some other means ofouter insulation. For example, the cable outer insulating jacket may beleft on this portion of interface cable 12, or if the outer jacket isremoved, a separate layer of shrinkable material may be applied aroundthis portion of interface cable 12.

FIG. 3 shows an alternate embodiment of splice portion 20 of terminalconnection device 10. In this embodiment, a first cable connector 24 isattached to one end of inner conductor 14 of interface cable 12. It maybe attached by any suitable method such as by crimping or with screws.In FIG. 3, it is attached by screws 25. First cable connector 24 isconfigured to mate with first socket 62 of conductive intermediateconnector 60. Intermediate connector 60 has a second socket 64configured to mate with second cable connector 26 which is attached toinner conductor 44 of a power cable 42. Second cable connector 26 andpower cable 42 are not part of the pre-assembled terminal connectiondevice 10. First and second cable connectors 24 and 26 and intermediateconnector 60 may optionally be enclosed by, and optionally securedwithin, a rigid sleeve (not included in FIG. 3), which may be insulativeor semiconductive.

As shown in FIG. 3, second stress control tube 36′ extends along thesplice portion of terminal connection device 10, including overconnector 24 and over a portion of intermediate connector 60. Aspreviously described, second stress control tube 36′ has a thin innersemiconductor layer (not shown) inside of stress control layer 38 alongthe portion of stress control layer 38 that will cover connectors 24 and26 (and intermediate connector 60). The length of the thin innersemiconductor layer is sufficient that it covers a portion of insulationlayer 16 of interface cable 12 and a portion of insulation layer 46 ofpower cable 42 when terminal connection device 10 is fully installed.The thin inner semiconductor layer may be painted on the interiorsurface of stress control layer 38 or may be a separate layer ofmaterial. Stress control tube 36′ also has a thin outer semiconductivelayer (not shown) on the outside of insulation layer 40. The thin outersemiconductive layer extends along the entire length of insulation layer40 of stress control tube 36′. The thin outer semiconductor layer may bepainted on the exterior surface of insulation layer 40 or may be aseparate layer of material. In the embodiment of FIG. 3, splice portion20 of terminal connection device 10 further comprises a tubular sleeve52 that extends over stress control tube 36′ from interface cable 12 topower cable 42. Tubular sleeve 52 comprises an insulating layer. Betweentubular sleeve 52 and second stress control tube 36′ there is typicallya “sock” 54 made of conducting or semiconducting material. Its purposeis to establish an electrical connection between semiconductive layers18 of interface cable 12 and semiconductive layer 48 (not shown) ofpower cable 42, respectively, when terminal connection device 10 isfully installed and to maintain the thin outer semiconductive layer (notshown) of second stress control tube 36′ at ground potential across thesplice.

As further illustrated in FIG. 3, prior to the mating of second cableconnector 26 with intermediate connector 60, both tubular sleeve 52 andstress control tube 36′ are folded back over intermediate connector 60,first cable connector 24, and interface cable 12 to allow for easyinsertion of second cable connector 26 into intermediate connector 60.First, a support core 57 is placed around tubular sleeve 52 generallyover first cable connector 24 and a portion of tubular sleeve 52 isfolded back and placed on support core 57, which holds the folded backportion of tubular sleeve 52 in an expanded state. Next, support core 55is placed over the folded back portion of tubular sleeve 52 and aportion of stress control tube 36′ is folded back and placed on supportcore 55, which holds the folded back portion of stress control tube 36′in an expanded state. After second cable connector 26 is mated withintermediate connector 60, support core 55 is removed and stress controltube 36′ is unfolded so that it covers second cable connector 26 andenough of power cable 42 such that stress control layer 38 overlaps thesemiconductive layer 48 (not shown) of power cable 42. Subsequently,support core 57 is removed and tubular sleeve 52 is unfolded so that itcovers stress control tube 36′ and a portion of the outer jacket ofpower cable 42 (not shown).

FIG. 4 is an alternate embodiment of the terminal portion 22 of terminalconnection device 10. In this embodiment, geometric stress control isemployed instead of a High K stress control material. Further, theterminal portion 22 comprises separable connector elements, whichprovides for a different type of connection than with a bare lug. FIG. 4shows a cable connector 72 attached to conductor 14 of interface cable12. Cable connector 72 is attached by any suitable means, typically bycrimping, and includes lug 34. Terminal portion 22 includes housing 82that generally defines first chamber 84 and second chamber 86. Firstchamber 84 and second chamber 86 intersect such that the interior offirst chamber 84 is in communication with the interior of second chamber86. First and second chambers 84,86 may intersect to form a generalT-shape as shown in FIG. 4 or a general L-shape (not shown). Housing 82may further include an outer semi-conductive layer 90 and anintermediate insulating layer 92, and an inner semi-conductive layer 94.As shown in FIG. 4, the inner semi-conducting layer 94 on the interiorwall of the first chamber 84 of the housing 82 makes intimate contactwith the cable connector 72. Preferably, the inner semi-conducting layer94 also makes intimate contact with the insulation layer 16 of interfacecable 12. A portion of the interior wall of first chamber 84 is made ofthe intermediate insulating layer 92. This portion preferably makesintimate contact with insulation layer 16. A portion of the interiorwall of first chamber 84 is made of outer semi-conducting layer 90. Thisportion preferably makes intimate contact with semiconductive layer 18.Tubular sleeve 52 is then positioned over at least a portion of outersemi-conducting layer 90 and interface cable 12. A stud (not shown) maybe inserted through the aperture in lug 34 and one or more matingdevices 96 may be inserted into second chamber 86 and attached to, orheld in position against, lug 34 by the stud.

Housing 82 may be made from any material suitable for cold-shrinkapplications. Most suitable are materials such as a highly elasticrubber material that has a low permanent set, such as ethylene propylenediene monomer (EPDM), elastomeric silicone, or a hybrid thereof. Thesemi-conductive and insulating materials may be made of the same ordifferent types of materials. The semi-conductive and insulatingmaterials may have differing degrees of conductivity and insulationbased on the inherent properties of the materials used or based onadditives added to the materials.

FIG. 5 is an alternate embodiment of the terminal portion 22 of terminalconnection device 10. In this embodiment, voltage and current sensorsare integrated in terminal portion 22. In the illustration of FIG. 5,insulating layer 16, semiconductive layer 18 of interface cable 12 aswell as the sensors and some related elements are not shown in crosssection while stress control tube 36, tubular sleeve 52, and insulatinglayer 107 are shown in cross section. As shown in FIG. 5, annular stripsof semiconductive layer 18 are removed to form non-conductive axialsections or gaps 100 in the semiconductor layer at which gaps theunderlying insulation layer 16 is exposed. The portions ofsemiconductive layer 18 separated by gaps 100 are labeled 18 a, 18 b,and 18 c for clarity. In an alternate embodiment, semiconductive layer18 may terminate with portion 18 a and pieces of a conductive orsemiconductive material may be positioned on interface cable 12 to servethe same functions as portions 18 b and 18 c of semiconductive layer 18.In another alternate embodiment, a conductive or semiconductive materialattached to the back of voltage sensor 102, prior to its attachment tointerface cable 12, may be used in place of portion 18 b ofsemiconductive layer 18. In yet another embodiment, voltage sensor 102is attached directly to the insulation layer of interface cable 12. Asillustrated in FIG. 5, a voltage sensor 102 is placed on semiconductivelayer portion 18 b, which is electrically isolated from portions 18 aand 18 c by gaps 100. Although the present specification refers toattaching a sensor to interface cable 12, in some embodiments, theinterface cable 12 itself functions as part of the sensor. In suchinstances, the reference herein to voltage sensor 102 refers to theportion of the sensor, e.g., a printed circuit board (PCB), which isattached to interface cable 12. In at least one embodiment of thepresent invention, the voltage sensor is a capacitive divider in which afirst capacitor consists of the cable inner conductor 14, the cableinsulation layer 16, and semiconductive portion 18 b. The secondcapacitor(s) are placed on a PCB, which is attached to semiconductivelayer portion 18 b. The inner electrical resistance of thesemiconductive layer portion 18 b is insignificant.

Strips of insulating material (not shown) cover gaps 100 to separatesemiconductive portion 18 b from any other conductive or semiconductivematerial or elements, except from the voltage sensor 102, and to preventthe presence of air in gaps 100, which air could cause a partialelectrical discharge and a failure of voltage sensor 102. The insulatingmaterial may be any suitable material such a combination of mastic,which will more easily fill gaps 100, and PVC tape placed over themastic. The PVC tape may also serve the purpose of attaching the voltagesensor 102 to interface cable 12. Voltage sensor 102 measures thevoltage of the inner conductor 14 of interface cable 12. A ground plate(not shown) of voltage sensor 102 is electrically connected to one orboth of semiconductive layer portions 18 a and 18 c by a conductiveelement 104, which may be a wire mesh that can be wrapped around one orboth of semiconductive layer portions 18 a and 18 c and soldered to aconnection point 106 on voltage sensor 102. If the portion of conductiveelement 104 bridging from semiconductive layer portions 18 a and 18 c tothe voltage sensor 102 are not insulated, the strips of insulatingmaterial (not shown) over gaps 100 will prevent it from makingelectrical contact with the underlying semiconductive portion 18 b.Insulation layer 107 covers voltage sensor 102 and the portions ofsemiconductive layer adjacent gaps 100. A layer of conductive orsemiconductor material (not shown) is placed over insulation layer 107.In at least one embodiment, the layer of conductive or semiconductivematerial is combined with insulative layer 107 so that insulative layer107 has an insulative layer facing the sensor and a layer of conductiveor semiconductive material facing stress control tube 36. The conductiveor semiconductive layer shields the sensor from external electricalfields. Stress control tube 36 covers insulation layer 107 and extendsto the end of interface cable 12 to which lug 34 is attached. Currentsensor 108 is positioned over semiconductive layer 18 adjacent tovoltage sensor 102. Wire 110 is connected to voltage sensor 102 and wire112 is connected to current sensor 108, which may be a Rogowski coil.Both wires 110, 112 are insulated so as not to cause any shorting. InFIG. 5, tubular sleeve 52″ extends along the entire length of thetermination portion 22 of terminal connection device 10 from lug 34 tothe splice portion of terminal connection device 10 where it overlapstubular sleeve 52′ of splice portion 20. Both wires 110, 112 passbetween the overlapped portions of tubular sleeve 52″ and tubular sleeve52′ to the outside of terminal connection device 10 where they may beconnected to, for example, an integrator, a measuring device, a controldevice, or other suitable types of devices.

In at least one embodiment, voltage sensor 102 comprises a double sidedflexible printed circuit board. As described herein, the top or front ofthe PCB is the portion that faces insulative layer 107. The top of thePCB typically includes conductive features that are electricallyconnected to external devices. The bottom or back of the PCB facesinterface cable 12. To establish the best possible electrical contactbetween sensor 102 and semiconductive layer portion 18 b, it isdesirable to maximize the contact area on the back of sensor 102. It wasfound that while a copper foil or gold-plated copper foil would work, apatterned gold-plated copper layer unexpectedly provided superiorresults over the alternatives. The pattern may be formed in any suitablemanner. For example, a photoresist process may be used to create thepattern by applying and developing a photoresist layer on the bottomcopper layer of the circuit board (and optionally on portions of the topcopper layer outside of the portion circuitized for the sensor tofunction) in a pattern that exposes areas of the copper layer to beremoved to create the desired copper pattern. The exposed portions ofthe copper layer(s) may then be exposed to a copper etchant solution toremove the exposed areas of copper. The patterned photoresist is thenremoved, leaving a pattern of copper on the bottom side of the circuitboard. A layer of nickel is then plated on the copper and gold or a goldalloy (sometimes referred hereinafter only as gold) is then plated onthe nickel layer. The patterned gold-plated copper layer of the PCBensures a good electrical connection between semiconductive layerportion 18 b and the conductive vias of the PCB that connect to theelectrical circuit elements on the top surface of the PCB. It was foundthat there was no significant amount of air trapped under the PCBbecause the patterned gold-plated copper layer on back of the PCB isembossed into semiconductive layer portion 18 b, thereby ensuringoptimal electrical contact between semiconductive layer portion 18 b andvoltage sensor PCB Output signals from the voltage sensor are on theorder of about 1 Volt with a current on the order of microamperes.

Like a solid layer, the patterned gold-plated copper layer of thepresent invention will provide an infinite amount of contact points. Thedistance from one contact point to another is insignificant, as it iswith a solid layer. The pattern created in the copper layer may be anysuitable pattern, including but not limited to, a grid with a square ordiamond shaped pattern. It is believed that a patterned gold-platedcopper layer is less likely to flake than a gold-plated plane such aswould exist if an unpatterned copper foil were gold plated. This isespecially an issue with thin, flexible PCBs, which are subject tomechanical stresses due to their ability to bend.

The voltage sensor PCB described herein differs from standard PCBs inthat standard PCBs have solder resist layers covering the front and backsurfaces of the PCB, except for conductive areas at which electricalcontact (typically by soldering) will be made. In the present voltagesensor 102, there is no solder resist on the bottom of the PCB. It isbelieved that the need for a solder layer on the back of the PCB, whichtypically inhibits the planar gold-plating from flaking, is not neededdue to the copper layer being patterned prior to gold plating. It isbelieved that the patterned copper layer more easily dissipatesmechanical stress than does a solid copper foil.

In addition to the foregoing, the use of the PCB in the presentapplication further limits the amount of mechanical stress applied tothe PCB. The PCB is subject to mechanical stress when it is bent andplaced around interface cable 12. Although this bent configuration mayplace some stress on the PCB, once it is affixed to interface cable 12,e.g., with a PVC tape, and especially after stress control tube 36 andtubular sleeve 52 are shrunk down around the interface cable 12, therebyapplying a radial force to the PCB of voltage sensor 102, the flexiblePCB remains in a relatively static state.

Although the invention has been described and illustrated with referenceto specific illustrative embodiments thereof, it is not intended thatthe invention be limited to those illustrative embodiments. Thoseskilled in the art will recognize that variations and modifications canbe made without departing from the true scope of the invention asdefined by the claims that follow. It is therefore intended to includewithin the invention all such variations and modifications as fallwithin the scope of the appended claims and equivalents thereof.

The invention claimed is:
 1. Terminal connection device for connectingan end of a medium- or high-voltage power cable to a connection point,the terminal connection device comprising: a) an interface cable havingfirst and second end portions, comprising an inner conductor and aconductive or semiconductive layer, b) a first stress control tubecomprising a stress control element, and an insulating layer arrangedaround the stress control element, wherein the first stress control tubeis mounted on the first end portion of the interface cable; c) a firstcable connector for connecting the interface cable to the power cable,the first cable connector being connected to the second end portion ofthe interface cable; d) one or more tubular shrinkable sleeves, at leasta portion of one of the tubular shrinkable sleeves extending over atleast a portion of the first stress control tube, wherein the portion ofthe tubular shrinkable sleeve extending over at least a portion of thefirst stress control tube is shrunk down around at least a portion ofthe first stress control tube, wherein the interface cable furthercomprises an insulating layer arranged concentrically around at least anaxial section of the inner conductor, and wherein the terminalconnection device comprises a capacitive voltage sensor including aprinted circuit board element, the printed circuit board element placedover an electrically isolated piece of conductive or semiconductivematerial, the electrically isolated piece of conductive orsemiconductive material arranged on the insulating layer of theinterface cable and operable to form an electrode of a sensing capacitorfor sensing a voltage of the inner conductor, and wherein the insulatinglayer is operable to form a dielectric of the sensing capacitor. 2.Terminal connection device according to claim 1, comprising a secondstress control tube, the second stress control tube comprising a stresscontrol element, and an insulating layer arranged around the stresscontrol element, wherein the second stress control tube is mounted overthe second end portion of the interface cable and at elast a portion ofthe first cable connector, and wherein at least a portion of one of thetubular shrinkable sleeves extends over at least a portion of the secondstress control tube.
 3. Terminal connection device according to claim 1,wherein the first cable connector is adapted to be connected to thepower cable by engagement between the first cable connector and a matingsecond cable connector mounted on an end of the power cable.
 4. Terminalconnection device according to claim 1, wherein a portion of at leastone of the tubular shrinkable sleeves is shrunk down around a portion ofthe interface cable.
 5. Terminal connection device according to claim 2,wherein the tubular shrinkable sleeve extending over at least a portionof the second stress control tube comprises a portion adapted to beshrunk down around a portion of the power cable.
 6. Terminal connectiondevice according to claim 1, wherein the first end portion of theinterface cable is attached to a lug.
 7. Terminal connection deviceaccording to claim 2, wherein the stress control element of one or bothof the first and second stress control tubes is a geometric stresscontrol element or a capacitive stress control element.
 8. Terminalconnection device according to claim 1, wherein the tubular shrinkablesleeve extending over at least a portion of the first stress controltube comprises, on an outer side, one or more skirts for reducingtracking current.
 9. Terminal connection device according to claim 1,wherein the terminal connection device further comprises additionalsemiconductive material, arranged concentrically around at least anaxial section of the insulating layer on either side of the electricallyisolated piece of conductive or semiconductive material, the additionalsemiconductive material comprising two semiconductive axial sections,electrically isolated from the electrically isolated piece of conductiveor semiconductive material by non-conductive axial sections. 10.Terminal connection device according to claim 1, wherein some or all ofthe electrically isolated piece of conductive or semiconductive materialor of the additional semiconductive material is affixed adhesively tothe insulating layer.
 11. Terminal connection device according to claim1, wherein the printed circuit board element comprises a patternedgold-plated copper layer in electrical contact with the electricallyisolated piece of conductive or semiconductive material.
 12. Terminalconnection device according to claim 1, wherein the electricallyisolated piece of conductive or semiconductive material comprises aportion of the semiconductive layer of the interface cable.
 13. Methodof connecting an end of a medium- or high-voltage power cable to aconnection point, comprising the steps of a) providing a terminalconnection device according to claim 1; b) providing a medium- orhigh-voltage power cable; c) connecting the terminal connection deviceto an end of the power cable by connecting the interface cable to theend of the power cable via the first cable connector; and d) connectingthe terminal connection device to the connection point by connecting thefirst end portion of the interface cable to the connection point.